I read some discussions that those old bitcoin movements can create fear on the market. People think those old bitcoins can be dumped on the market and will cause a price fall.
News outlets try to sell their articles by making them as sensational as possible, this involves crearin links and backstories which would be a bit more attractive to the average reader along with a click bait headline.
Bitcoins being moved from one wallet to the other, from wallet to exchange or the other way around should not be a topic of discussion, but the media would use a headline which highlights that a long term holder has finally lost faith in bitccoin and is ready to sell their bags, with maybe a question if we would see Satoshi's stash move anytime soon.
I don't think those old bitcoins are enough to dump the market. Those coins and movements only cause uncertainty and affect people with weak mentality.
They don't even cause uncertainty, such discussions only last for a few hours or at most a day before it's no longer a topic.